The parasitic protozoan Giardia lamblia, which is a major cause of waterborne enteric disease (giardiasis) throughout the world, exists in two morphologic forms, the active trophozoite and the dormant cyst. Trophozoites colonize the upper part of the human small intestine and cause disease, whereas the cyst form survives outside the host and is responsible for transmission. The main goal of this laboratory is to understand the cellular and molecular mechanisms of differentiation as well as the host-parasite interactions by Giardia.